David - ETP is NOT the midpoint between the 2 airfields, unless there's no wind, which ain't very likely. The ETP always moves into wind - if you're flying over the Atlantic, where there's almost always a westerly wind blowing at cruise height, the ETP will be closer to Gander than to Shannon. This is because your groundspeed is lower when you're flying into the wind and, conversely, higher when you're flying downwind.
And yes, the 330's FMS will do the calculations for you, I imagine the chart is a hangover from The Old Days when you had to do such things for yourself.
Hope this helps.
[This message has been edited by tired (edited 21 October 2000).]